Rocket chemical found in lettuce

Scientist not alarmed by oxidant's path through Colorado River water to Arizona, California fields.

Larry Copenhaver
Tucson Citizen
Feb 02, 2004 (Tucson Citizen)

A chemical used as an oxidant in rocket fuels has been detected in some samples of leafy vegetables irrigated with Colorado River water, said a University of Arizona research scientist.

The chemical, perchlorate, apparently seeped into the river from a rocket fuel factory outside Las Vegas, said Charles Sanchez, director of the Yuma Agricultural Center, part of the UA College of Agriculture and Life Sciences.

Mixed with the river water, the chemical flowed south and into irrigation canals and fields in California and Arizona, he said. There, traces were taken up by the roots of plants and deposited in leaves.

Contaminants were found in the outside leaves and sometimes in the pithy framework of lettuce, not in the tender leaves people eat, he said.

"We are not particularly alarmed by the findings," Sanchez said, referring to a study funded by the Arizona Iceberg Lettuce Research Council. "We think the risk is minimal or nonexistent."

And there is no reason to avoid eating vegetables from plants irrigated with Colorado River water, he said. "I eat salads every day."

Although romaine lettuce also showed traces of the chemical, other vegetables tested, such as corn and peppers, showed no detectable levels.

The impetus for the research was a concern that perchlorate would make its way into the human food chain through vegetables such as broccoli, cauliflower and lettuce, he said. It affects humans by inhibiting the thyroid's uptake of iodine.

Perchlorate levels in water have been measured as high as 14 parts per billion, detected at Lake Mead, the reservoir behind Hoover Dam, Sanchez said from his Yuma office in a phone interview. It appears that microbial organisms capable of reducing perchlorate to chloride are fairly widespread.

Sanchez cautioned that the data were preliminary and more work needs to be done. "We have a long way to go in our research, but it appears contamination levels are below that that would be dangerous."

Other important research needed is to evaluate the extent to which perchlorate has accumulated in soils and to what extent it has tainted groundwater, he said.

Meanwhile, there is a debate over the suitable standard of perchlorate in water and how much is safe for human consumption.